Pattern-equivariant homology

Walton, James

doi:10.2140/agt.2017.17.1323

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Pattern-equivariant homology

James J Walton

Algebraic & Geometric Topology 17 (2017) 1323–1373

DOI: 10.2140/agt.2017.17.1323

Abstract

Pattern-equivariant (PE) cohomology is a well-established tool with which to interpret the Čech cohomology groups of a tiling space in a highly geometric way. We consider homology groups of PE infinite chains and establish Poincaré duality between the PE cohomology and PE homology. The Penrose kite and dart tilings are taken as our central running example; we show how through this formalism one may give highly approachable geometric descriptions of the generators of the Čech cohomology of their tiling space. These invariants are also considered in the context of rotational symmetry. Poincaré duality fails over integer coefficients for the “ePE homology groups” based upon chains which are PE with respect to orientation-preserving Euclidean motions between patches. As a result we construct a new invariant, which is of relevance to the cohomology of rotational tiling spaces. We present an efficient method of computation of the PE and ePE (co)homology groups for hierarchical tilings.

Keywords

aperiodic order, tilings, quasicrystals, tiling cohomology

Mathematical Subject Classification 2010

Primary: 52C23

Secondary: 37B50, 52C22, 55N05

References

Publication

Received: 10 February 2014

Revised: 22 September 2016

Accepted: 25 October 2016

Published: 17 July 2017

Authors

James J Walton
Department of Mathematics University of York Heslington YO10 5DD United Kingdom
http://maths.york.ac.uk/www/jjw548

Volume 17, issue 3 (2017)